Primary and secondary $\gamma$ rays following thermal and $p$-wave resonant (2.96 eV) neutron capture on ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}$ were measured to study $\gamma$-ray transitions in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$. Average resonance capture spectra at 2 and 24 keV were also recorded and the ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}(n,\gamma \mathrm{ce})$ reaction was studied and transition multipolarities were deduced. A detailed level scheme up to ∼1400 keV has been constructed. Numerous spin assignments have been revised, leading to substantial changes in the ($d,p$) and ($d,t$) spectroscopic factors, in particular for the $g_{\frac{7}{2}}$ orbit. The data on primary transition intensities for the 2.96 eV resonance are compared with the valence neutron capture model. The level scheme deduced for ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$ sheds new light on the previously proposed $g_{\frac{7}{2}}-h_{\frac{11}{2}}$ anomaly in the filling of these orbits, suggesting that, at least in ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$, the appearance of the anomaly was largely due to spin misassignments. The revised systematics in the occupation of shell model orbits for a number of nuclei in this mass region is reviewed. Within the level scheme is a group of low-spin negative-parity levels which belong to the same family as the high-spin, decoupled, unique-parity states known in other odd mass Pd isotopes. These states correspond to the favored and unfavored anti-aligned levels for core rotations $R\le 6$. Calculations in the framework of the particle-rotor model cannot reproduce these level energies.

NUCLEAR REACTIONS ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}(n,\gamma )$, $E=\mathrm{thermal},2.96 \mathrm{eV},2\mathrm{} \mathrm{KeV},24 \mathrm{KeV}$; measured $E_{\gamma }$, $I_{\gamma }$, $I_{\gamma } \left(\theta \right)$; ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}(n,\gamma \mathrm{ce}){}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}$ ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$ deduced $J$, $\pi$ of 2.96 eV resonance, levels, transitions, multipolarities, $J$, $\pi$. Ge(Li) detectors, three crystal spectrometer, curved crystal spectrometers, conversion electron spectrometer, enriched targets.

NUCLEAR STRUCTURE ${}_{}{}^{109}{}_{}{}^{}\mathrm{Pd}$ revised ($d,p$), ($d,t$) spectroscopic factors, negative-parity anti-aligned favored and unfavored levels, particle-rotor model.

• Received 5 July 1979

DOI:https://doi.org/10.1103/PhysRevC.21.65